Just to be sure, this will detect salinity fluctuations of coastal marine water (35 ppt)?!

The max salinity for this meter is 9.99g/L (parts per thousand). So if you know the water is in the range of 35ppt, you can't make direct measurements. But, you could dilute the sample (say 10x) in the field using bottled water (has a salinity <<< sample) or DI water and that would put you at 3.5g/L roughly. You should be able to detect fluctuations at 0.1ppt on the diluted water which translates into detecting 1ppt fluctuations in the water.

Brand	EXTECH
Model Number	EC150
Product Dimensions	16.51 x 3.56 x 3.3 cm; 100 g
Name List for Name Plates	導電率 \| TDS
Material	プラスチック
Quantity	1
Are Batteries Included	Yes
Battery Type	Alkaline
Item Weight	100 g

Extechメーター

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